Claus process for sulfur recovery with intermediate water vapor removal by adsorption

ABSTRACT

A method to recover sulfur comprising the steps of feeding an acid gas stream to a combustion furnace, condensing the cooled furnace stream to produce a first gas stream, feeding the first gas stream to a first adsorber comprises a molecular sieve, feeding the first hot dry gas stream to a first catalytic reactor, cooling the first catalytic outlet stream in a first condenser, feeding the second gas stream to a second adsorber, feeding the second hot dry gas stream to a second catalytic reactor, cooling the second catalytic outlet stream in a second condenser, introducing the third gas stream to a third adsorber, feeding the third hot dry gas stream to a third catalytic reactor to produce a third catalytic outlet stream, and cooling the third catalytic outlet stream in a third condenser to produce a third sulfur stream and a tail gas stream.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/988,032, filed on Jan. 5, 2016. For purposes of United States patentpractice, this application incorporates the contents of the applicationby reference in its entirety.

TECHNICAL FIELD

Disclosed are methods for sulfur recovery.

BACKGROUND

Sulfur recovery refers to the conversion of hydrogen sulfide (H₂S) toelemental sulfur. Hydrogen sulfide is a byproduct of processing naturalgas and refining high-sulfur crude oils. The conventional method ofsulfur recovery is the Claus process. Approximately 90 percent to 95percent (%) of recovered sulfur is produced by the Claus process. Aconventional Claus process can recover between 95% and 98% of thehydrogen sulfide.

The conventional Claus process includes a thermal combustion stage and acatalytic reaction stage. In terms of equipment, the Claus plant (Clausunit) includes a thermal reactor and two or three catalytic reactors(Claus converters). Typical sulfur recovery efficiencies for Clausplants with two Claus converters (reactors) is between 90 and 97%, andfor a Claus plant with three converters between 95 and 98%. But there isincreasing demand to achieve higher sulfur removal and recoveryefficiency due to tight emissions regulations. Recent environmentalregulations regarding sulfur oxides (SOx) emissions place a stringentrequirement on commercial sulfur recovery and accordingly, mostcountries require sulfur recovery efficiency in the range of 98.5% to99.9% or higher.

The addition of a tail-gas treatment unit (TGTU) can increase sulfurrecovery to or above 99.9%, but requires complex and expensiveequipment. The TGTU entails either an add-on unit at the end of theClaus unit or a modification to the Claus unit itself. The add-on TGTUat the end of the Claus unit is generally used when the Claus processincludes two Claus converters. Although there are several varieties oftail gas treatment technologies, they can be grouped into the followingfour broad categories: sub-dew point Claus process, direct oxidation ofH₂S to sulfur, sulfur dioxide (SO₂) reduction and recovery of H₂S, andH₂S combustion to SO₂ and recovery of SO₂.

Sub-dew point Claus processes are processes based on a Claus converterperforming at temperatures below the sulfur dew point (lower temperatureis desirable due to equilibrium nature of the Claus catalytic reaction).Sub-dew point processes provide high equilibrium conversions in onecatalyst bed, but are complicated by the need for periodic catalystregeneration by sulfur evaporation at elevated temperatures. Toaccommodate for regeneration, such processes are usually performed intwo or three (or even more) parallel reactors, periodically undergoingreaction and regeneration. Cold-bed-adsorption (CBA) is the mostefficient sub-dew point process and can achieve 99% sulfur recovery.

Processes involving direct oxidation of H₂S to sulfur are based onselective oxidation of H₂S by oxygen to elemental sulfur using selectivecatalysts.

TGTU technology based on SO₂ reduction and recovery of H₂S involves thecatalytic hydrogenation of leftover sulfur species to H₂S, absorption ofthe H₂S with amine solution and then recycling the H₂S back to the Clausfurnace.

TGTU technology based on H₂S combustion to SO₂ and recovery of SO₂involves the combustion of leftover H₂S in the tail gas stream to SO₂,absorption of SO₂ with a solvent (wet scrubbing), and recycling the SO₂back to the feed to Claus plant. Although SO₂ scrubbing, also known asflue gas scrubbing, has not been commercially tested as a TGTU, thetechnology has been extensively used as flue gas scrubbing for coalbased power stations.

SUMMARY

Disclosed are methods for sulfur recovery.

In a first aspect, a method to recover sulfur from hydrogen sulfide inan acid gas stream is provided. The method includes the steps of feedingthe acid gas stream to a combustion furnace to produce a furnace outletstream. The combustion furnace configured to convert the hydrogensulfide to elemental sulfur, where the furnace outlet stream includeselemental sulfur, hydrogen sulfide, sulfur dioxide, and water vapor. Thestep of introducing the furnace outlet stream to a waste heat boiler toproduce a cooled furnace outlet stream, the waste heat boiler configuredto reduce a temperature of the furnace outlet stream, condensing thecooled furnace stream in a sulfur condenser to produce a liquid sulfurstream and a first gas stream, the sulfur condenser configured to reducea temperature of the cooled furnace stream to a temperature below a dewpoint of elemental sulfur and above a dew point of water, feeding thefirst gas stream to a first adsorber to produce a first dry gas streamand a first water stream, wherein the first adsorber includes amolecular sieve, wherein the first dry gas stream is in the absence ofwater vapor, wherein the first dry gas stream includes hydrogen sulfideand sulfur dioxide. The method further including the steps of heatingthe first dry gas stream in a first reheater to produce a first hot drygas stream, wherein the first hot dry gas stream is at a firsttemperature, feeding the first hot dry gas stream to a first catalyticreactor to produce a first catalytic outlet stream, wherein the firstcatalytic outlet stream includes elemental sulfur, hydrogen sulfide,sulfur dioxide, and water vapor, cooling the first catalytic outletstream in a first condenser to produce a first sulfur stream and asecond gas stream, the first condenser configured to condense theelemental sulfur in the first catalytic outlet stream such that thefirst sulfur stream includes liquid sulfur, wherein a temperature in thefirst condenser is between the dew point of sulfur and the dew point ofwater, wherein the second gas stream includes hydrogen sulfide, sulfurdioxide, and water vapor, feeding the second gas stream to a secondadsorber to produce a second dry gas stream and a second water stream,wherein the second adsorber includes a molecular sieve, wherein thesecond dry gas stream includes hydrogen sulfide and sulfur dioxide,wherein the second dry gas stream is in the absence of water vapor,heating the second dry gas stream in a second reheater to produce asecond hot dry gas stream. The second hot dry gas stream is at a secondtemperature, where the second temperature is lower than the firsttemperature. The method further includes the steps of feeding the secondhot dry gas stream to a second catalytic reactor to produce a secondcatalytic outlet stream, wherein the second catalytic outlet streamincludes elemental sulfur, hydrogen sulfide, sulfur dioxide, and watervapor, cooling the second catalytic outlet stream in a second condenserto produce a second sulfur stream and a third gas stream, the secondcondenser configured to condense the elemental sulfur in the secondcatalytic outlet stream such that the second sulfur stream includesliquid sulfur, wherein a temperature in the second condenser is betweenthe dew point of sulfur and the dew point of water, wherein the thirdgas stream includes hydrogen sulfide, sulfur dioxide, and water vapor,introducing the third gas stream to a third adsorber to produce a thirddry gas stream and a third water stream, wherein the third adsorberincludes a molecular sieve, wherein the third dry gas stream includeshydrogen sulfide and sulfur dioxide, wherein the third dry gas stream isin the absence of water vapor, heating the third dry gas stream in athird reheater to produce a third hot dry gas stream. The third hot drygas stream is at a third temperature, where the third temperature islower than the second temperature. The method further including thesteps of feeding the third hot dry gas stream to a third catalyticreactor to produce a third catalytic outlet stream, wherein the thirdcatalytic outlet stream includes elemental sulfur, hydrogen sulfide,sulfur dioxide, and water vapor, and cooling the third catalytic outletstream in a third condenser to produce a third sulfur stream and a tailgas stream, the third condenser configured to condense the elementalsulfur in the third catalytic outlet stream such that the third sulfurstream includes liquid sulfur, wherein a temperature in the thirdcondenser is between the dew point of sulfur and the dew point of water,wherein the tail gas stream includes hydrogen sulfide, sulfur dioxide,and water vapor.

In certain aspects of the present invention, a total conversion can bedetermined. In certain aspects of the present invention, the totalconversion exceeds 99% by weight. In certain aspects of the presentinvention, the molecular sieve is molecular sieve 3A. In certain aspectsof the present invention, the first temperature is 235° C. In certainaspects of the present invention, the second temperature is 215° C. Incertain aspects of the present invention, the third temperature is 205°C.

In a second aspect of the present invention, a system to recover sulfurfrom hydrogen sulfide in an acid gas stream is provided. The systemincludes a combustion furnace, the combustion furnace configured toconvert the hydrogen sulfide to elemental sulfur to produce a furnaceoutlet stream, wherein the furnace outlet stream includes elementalsulfur, hydrogen sulfide, sulfur dioxide, and water vapor, a waste heatboiler fluidly connected to the combustion furnace, the waste heatboiler configured to remove heat from the furnace outlet stream toproduce a cooled furnace stream, a sulfur condenser fluidly connected tothe waste heat boiler, the sulfur condenser configured to condense theelemental sulfur in cooled furnace stream to produce a liquid sulfurstream and a first gas stream, wherein the gas stream is in the absenceof elemental sulfur, wherein the first gas stream includes water vapor,a first adsorber fluidly connected to the sulfur condenser, the firstadsorber configured to remove water vapor from the first gas stream toproduce a first dry gas stream and a first water stream, wherein thefirst adsorber includes a molecular sieve, wherein the first dry gasstream includes hydrogen sulfide and sulfur dioxide and is in theabsence of water vapor, a first Claus catalytic stage fluidly connectedto the first adsorber, the first Claus catalytic stage configured toproduce a first sulfur stream and a second gas stream, a second adsorberfluidly connected to the first Claus catalytic stage, the secondadsorber configured to remove water vapor from the second gas to producea second dry gas stream, wherein the second adsorber includes amolecular sieve, wherein the second dry gas stream includes hydrogensulfide and sulfur dioxide and is in the absence of water vapor, asecond Claus catalytic stage fluidly connected to the second adsorber,the second Claus catalytic stage configured to produce a second sulfurstream and a third gas stream, a third adsorber fluidly connected to thesecond Claus catalytic stage, the third adsorber configured to removewater vapor from the third gas to produce a third dry gas stream,wherein the third adsorber includes a molecular sieve, wherein the thirddry gas stream includes hydrogen sulfide and sulfur dioxide and is inthe absence of water vapor, and a third Claus catalytic stage fluidlyconnected to the third adsorber, the third Claus catalytic stageconfigured to produce a third sulfur stream and a tail gas stream.

In certain aspects of the present invention, a total conversion can bedetermined. In certain aspects of the present invention, the totalconversion exceeds 99% by weight. In certain aspects of the presentinvention, the molecular sieve is molecular sieve 3A. In certain aspectsof the present invention, the first Claus catalytic stage includes afirst reheater fluidly connected to the first adsorber, the firstreheater configured to increase a temperature of the first dry gasstream to produce a first hot dry gas stream, wherein the first hot drygas stream is at a first temperature, a first catalytic reactor fluidlyconnected to the first reheater, the first catalytic reactor configuredto convert hydrogen sulfide and sulfur dioxide to elemental sulfur toproduce a first catalytic outlet stream, wherein the first catalyticoutlet stream includes hydrogen sulfide, sulfur dioxide, elementalsulfur and water, and a first condenser, the first condenser fluidlyconnected to the first catalytic reactor, the first condenser configuredto condense the elemental sulfur in the first catalytic outlet stream toproduce a first sulfur stream and the second gas stream, wherein thesecond gas stream includes hydrogen sulfide, sulfur dioxide, and watervapor. In certain aspects of the present invention, the firsttemperature is 235° C. In certain aspects of the present invention, thesecond Claus catalytic stage includes a second reheater fluidlyconnected to the second adsorber, the second reheater configured toincrease a temperature of the second dry gas stream to produce a secondhot dry gas stream, wherein the second hot dry gas stream is at a secondtemperature, a second catalytic reactor fluidly connected to the secondreheater, the second catalytic reactor configured to convert hydrogensulfide and sulfur dioxide to elemental sulfur to produce a secondcatalytic outlet stream, wherein the second catalytic outlet streamincludes hydrogen sulfide, sulfur dioxide, elemental sulfur and water,and a second condenser, the second condenser fluidly connected to thesecond catalytic reactor, the second condenser configured to condensethe elemental sulfur in the second catalytic outlet stream to produce asecond sulfur stream and the second gas stream, wherein the second gasstream includes hydrogen sulfide, sulfur dioxide, and water vapor. Incertain aspects of the present invention, the second temperature is 215°C. In certain aspects of the present invention, the third Clauscatalytic stage includes a third reheater fluidly connected to the thirdadsorber, the third reheater configured to increase a temperature of thethird dry gas stream to produce a third hot dry gas stream, wherein thethird hot dry gas stream is at a third temperature, a third catalyticreactor fluidly connected to the third reheater, the third catalyticreactor configured to convert hydrogen sulfide and sulfur dioxide toelemental sulfur to produce a third catalytic outlet stream, wherein thethird catalytic outlet stream includes hydrogen sulfide, sulfur dioxide,elemental sulfur and water, and a third condenser, the third condenserfluidly connected to the third catalytic reactor, the third condenserconfigured to condense the elemental sulfur in the third catalyticoutlet stream to produce a third sulfur stream and the third gas stream,wherein the third gas stream includes hydrogen sulfide, sulfur dioxide,and water vapor. In certain aspects of the present invention, the thirdtemperature is 205° C.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the inventive scopewill become better understood with regard to the following descriptions,claims, and accompanying drawings. It is to be noted, however, that thedrawings illustrate only several embodiments and are therefore not to beconsidered limiting of the invention's scope.

FIG. 1 is a process flow diagram of the process of the present inventionincluding three adsorbers.

FIG. 2 is a process flow diagram of a conventional Claus process havingtwo catalytic reactors.

FIG. 3 is a process flow diagram of a conventional Claus process havingthree catalytic reactors.

FIG. 4 is a process flow diagram of the process of the present inventionincluding one adsorber.

FIG. 5 is a process flow diagram of the process of the present inventionincluding two adsorbers.

FIG. 6 is a process flow diagram of the process of the present inventionincluding one adsorber.

FIG. 7 is a process flow diagram of the process of the present inventionincluding one adsorber.

FIG. 8 is a process flow diagram of the process of the present inventionincluding two adsorber.

FIG. 9 is a process flow diagram of the process of the present inventionincluding one adsorbers.

FIG. 10 is a process flow diagram of an adsorber.

FIG. 11 is a depiction of the isotherms for water vapor on molecularsieve 3A.

DETAILED DESCRIPTION

While the inventive scope will be described with several embodiments, itis understood that one of ordinary skill in the relevant art willappreciate that many examples, variations and alterations to theapparatus and methods described herein are within the scope and spiritof the invention. Accordingly, the embodiments described are set forthwithout any loss of generality, and without imposing limitations, on theclaimed invention. Those of skill in the art understand that theinventive scope includes all possible combinations and uses ofparticular features described in the specification.

The present invention provides a method for recovering elemental sulfurfrom an acid gas stream containing hydrogen sulfide. The method is animprovement to the conventional Claus process. The method of the presentinvention advantageously increases the amount of elemental sulfurrecovered and therefore reduces the amount of sulfur dioxide vented toatmosphere over a conventional Claus process. Thus, the presentinvention enables a Claus process to meet more stringent sulfurregulations.

As used herein, and unless otherwise specified the term “elementalsulfur” refers to sulfur vapor, which can be present as S₂, S₃, S₄, S₅,S₆, S₇, and S₈, due to simple polymerization. Without being bound to aparticular theory, it is noted that high reaction temperatures favor theproduction of S₂ and lower reaction temperatures favor formation of S₈.

As used herein, “dew point” refers to the temperature of saturation of avapor with a liquid. It is the temperature at which liquid evaporates atthe same rate at which it condenses. Dew point for any compound is afunction of the pressure and the composition of the vapor, includingfraction of compound in the vapor. Below the dew point of a component,the component will condense from the vapor phase.

The method of the present invention incorporates removal of water vapor(H₂O) to drive the Claus catalytic reaction toward conversion toelemental sulfur. The Claus catalytic reaction occurs in the catalyticreactors of the Claus process, according to the following equation:

$\begin{matrix}{\left. {{2H_{2}S} + {SO}_{2}}\leftrightarrows{{\frac{3}{8}S_{8}} + {2H_{2}O}} \right.;{{\Delta\; H} = {{- 108}\mspace{14mu}{{kJ}/{mol}}}}} & (1)\end{matrix}$

where, S₈ is a form of elemental sulfur and ΔH is the change in enthalpyand the negative value indicates that the reaction is exothermic.Reaction (1), the Claus catalytic reaction, is a reversible exothermicreaction. The extent of reaction is limited by the equilibrium value.One way to drive the reaction toward the right is to lower thetemperature. However, the ability to reduce the temperature is limitedby the sulfur dew point. Temperatures below the sulfur dew point leadsto sulfur condensation in the catalyst bed of the catalytic reactor.Sulfur condensation can lead to impairment of the catalyst surface andto catalyst deactivation. As a result, the temperature in the catalyticreactors is maintained at a temperature between 5° C. and 10° C. abovethe sulfur dew point. Sulfur condenses at temperatures at or below 175°C., alternately at temperatures between 175° C.-200° C., and alternatelyat temperatures at or below 200° C. Conventional Claus units aredesigned such that the lowest reaction temperature is only reached inthe last catalytic reactor in the catalytic reaction stage.

Another way to increase conversion to elemental sulfur in reaction (1)is to remove reaction products from the reaction medium. The removal ofreaction products results in a higher conversion in an equilibriumreaction. The conventional Claus process focuses on the removal ofsulfur by performing reaction (1) in a series of two or three catalyticreactors that include intermediate removal of sulfur in condensers. Thepresent invention advantageously incorporates the additional step ofselective removal of water between catalytic reactors to improve theequilibrium in the Claus catalytic reaction. The selective removal ofwater can shift reaction (1) further to the right due to the secondorder dependency of the equilibrium constant on water vapor partialpressure as shown in the following equation:

$\begin{matrix}{{{K_{eq}(t)} = \frac{\left( P_{H_{2}O}^{2} \right)\left( P_{S_{8}}^{\frac{3}{8}} \right)}{\left( P_{H_{2}S}^{2} \right)\left( P_{{SO}_{2}} \right)}},} & (2)\end{matrix}$

where, P_(H2O) is the partial pressure of water, P_(S8) is the partialpressure of sulfur, P_(H2S) is the partial pressure of hydrogen sulfideand P_(SO2) is the partial pressure of sulfur dioxide and Keq is theequilibrium constant. Reaction (2) has a water vapor partial pressuredependency of power to 2, while a sulfur partial pressure dependency ofpower to ⅜. Without being bound by a particular theory, it is understoodthat equilibrium constant, K_(eq) is function of temperature, such thatat a given temperature, the value of K_(eq) is fixed. When equilibriumis disturbed, for example by removing either products or reactants, thereaction will shift to counterbalance the disturbance (that is tore-establish the equilibrium).

The method of the present invention incorporates the removal of watervapor in the catalytic reaction stage of the Claus process. The methodfor recovering sulfur includes an adsorber placed upstream from one ormore of the catalytic reactors of the Claus unit.

An acid gas stream and an air feed are fed to a combustion furnace (theClaus thermal stage), where hydrogen sulfide, sulfur dioxide, and oxygenform elemental sulfur according to the Claus thermal reactions, shown inthe following equations:

$\begin{matrix}{\left. {{H_{2}S} + {\frac{3}{2}O_{2}}}\rightarrow{{H_{2}O} + {SO}_{2}} \right.;{{\Delta\; H} = {{- 44}\mspace{14mu}{{kJ}/{mol}}}}} & (3)\end{matrix}$

$\begin{matrix}{\left. {{2H_{2}S} + {SO}_{2}}\rightarrow{{\frac{3}{2}S_{2}} + {2H_{2}O}} \right.;{{\Delta\; H} = {56\mspace{14mu}{{kJ}/{mol}}}}} & (4)\end{matrix}$

Reaction (3), a combustion reaction is exothermic indicated by thenegative ΔH. Reaction (4), the thermal Claus reaction, is a reversible,endothermic reaction, indicated by the positive ΔH. The SO₂ can be fromany source capable of providing SO₂ to be consumed in reaction (4).Examples of sources of SO₂ include being produced in reaction (3), beinga component of the acid gas stream, being present as a result of aseparate feed to the combustion furnace that contains SO₂, and acombination of the same.

The acid gas stream can be from any source that produces a streamcontaining hydrogen sulfide (H₂S). The acid gas stream can include H₂S,carbon dioxide (CO₂), other gases, and combinations of the same. Theother gases can include carbon monoxide (CO), water (H₂O), nitrogen(N₂), hydrogen (H₂), and combinations of the same. The nature andcomposition of the acid gas stream depends on the process that is thesource for the acid gas stream and can be determined using anytechnology capable of analyzing the composition of an acid gas feedstream.

The air feed can be any oxygen (O₂) containing gas suitable for use inthe combustion furnace. Example gases suitable for use as the air feedinclude air, oxygen-enriched air, pure O₂, or any combination thereof.In at least one embodiment, the air feed is air.

In at least one embodiment, the air feed is adjusted such that one-thirdof the H₂S present in the acid gas stream is burned to create SO₂ asshown in reaction (3) and 60%-70% of the remaining H₂S is converted toelemental sulfur according to reaction (4). The combustion furnace canbe any process unit capable of supporting the high temperatures of theClaus thermal reactions, reactions (3) and (4). The combustion furnaceoperates at a temperature in the range of 900° C. to 1400° C. In atleast one embodiment, the temperature in the combustion furnace isgreater than 985° C. Without being bound to a particular theory, attemperatures greater than 985° C. reaction (4), the endothermicformation of elemental sulfur is favored. The Claus thermal reactionsconvert between 60% by weight and 70% by weight of the hydrogen sulfideand sulfur-containing compounds present in the acid gas stream toelemental sulfur. A furnace outlet stream exits the combustion furnace.The furnace outlet stream can include H₂S, SO₂, CO₂, H₂O, elementalsulfur, other gases, and combinations of the same.

The furnace outlet stream exits the combustion furnace and is introducedto a waste heat boiler. The furnace outlet stream is at a temperaturebetween 980° C. and 1200° C. The waste heat boiler can be any heatexchanger capable of removing heat from a stream and producing steam.The steam produced in the waste heat boiler can be high pressure steam(above 40 atm (4053 kPa)) or medium pressure stream (about 20 atm(2026.5 kPa). In at least one embodiment, the waste heat boiler produceshigh pressure steam. The waste heat boiler removes heat from the furnaceoutlet stream to produce a cooled furnace stream.

The cooled furnace stream is in a gas state. The cooled furnace streamis fed to a sulfur condenser. The sulfur condenser removes heat from thecooled furnace stream causing the elemental sulfur present in the cooledfurnace stream to condense and form a liquid sulfur stream. Thetemperature in the sulfur condenser is between 100° C. and 200° C.,alternately between 110° C. and 200° C., 120° C. and 200° C., 130° C.and 200° C., and 140° C. and 200° C. The liquid sulfur stream cancontain between 60 weight % and 75 weight % of the sulfur in the acidgas stream, and alternately between 65 weight % and 70 weight % of thesulfur in the acid gas stream.

The components present in the cooled furnace outlet stream that do notcondense leave the sulfur condenser as a first gas stream. The first gasstream can contain H₂S, SO₂, CO₂, H₂O, process gases, and combinationsof the same.

Referring to FIGS. 1-9, acid gas stream 100, air feed 102, furnaceoutlet stream 103, cooled furnace outlet stream 105, liquid sulfurstream 108, and first gas stream 106 can be understood. Combustionfurnace 3, waste heat boiler 5, and sulfur condenser 6 can also beunderstood.

In a conventional Claus process, the first gas stream is fed to a seriesof two to three Claus catalytic stages. Each of the Claus catalyticstages includes a reheater, a catalytic reactor, and a condenser. Thereheaters can be any heat exchanger capable of heating a gas stream fromthe condenser outlet temperature to the temperature at which the Clauscatalytic reactions in the catalytic reactors occur. Due to theexothermic nature of reaction (1), the catalytic reactor temperature islower in each subsequent catalytic reactor than the previous catalyticreactor. Without being bound to a particular theory, it is understoodthat the lower temperature in each subsequent catalytic reactor takesadvantage of the equilibrium nature of the reaction. The reactiontemperature of the first catalytic reactor is the highest in order toconvert other sulfur species. The first reheater can heat the first gasstream to a first temperature above about 205° C., alternately betweenabout 205° C. and about 340° C., alternately between about 215° C. andabout 340° C., and alternately between about 225° C. and about 340° C.In at least one embodiment, the first temperature is about 235° C. Thesecond reheater can heat the second gas stream to a second temperaturebetween 5 and 25 degrees below the first temperature, alternatelybetween 10 and 20 degrees below the first temperature, and alternatelybetween 15 and 20 degrees below the first temperature. In at least oneembodiment, the second temperature is 20 degrees less than the firsttemperature. In at least one embodiment, the second temperature is 20degrees less than the first temperature and the second temperature is215° C. The third reheater can heat the third gas stream to a thirdtemperature between 5 and 25 degrees below the second temperature,alternately between 10 and 20 degrees below the second temperature, andalternately between 15 and 20 degrees below the second temperature. Inat least one embodiment, the second temperature is 10 degrees less thanthe first temperature. In at least one embodiment, the secondtemperature is 10 degrees less than the first temperature and the secondtemperature is 205° C. The specific temperature in each reheater can bedesigned based on the overall system.

In the catalytic reactors, the hydrogen sulfide and sulfur dioxide areconverted to elemental sulfur and water according to reaction (1). Thecatalytic reactors include a catalyst bed. The catalyst in the catalystbed of the catalytic reactors can be any catalyst that catalyzesreaction (1). The catalyst can include alumina, titanium dioxide, orcombinations thereof. Without being bound to a particular theory, it isobserved that reaction (1) produces primarily S₈ from the reactants H₂Sand SO₂, whereas reaction (4) produces primarily S₂. One of skill in theart will understand that both forms of sulfur, S₂ and S₈, arerecoverable as liquid sulfur. A catalytic outlet stream exits each ofthe catalytic reactors and is fed to the condensers. The catalyticoutlet stream can include elemental sulfur, H₂S, H₂O, SO₂, other gases,and combinations of the same.

The condensers can be any heat exchanger capable of cooling each of thecatalytic outlet streams to a temperature at which sulfur condenses toproduce a sulfur stream, but above which water remains as a vapor. Thesulfur stream includes liquid sulfur. In at least one embodiment, thetemperature in the condensers is between 101° C. and 200° C. Thecondensers can be designed to cool to temperatures at which all of thesulfur is removed.

The Claus catalytic stages can be understood with reference to FIGS. 2and 3. FIG. 2 depicts a system with two Claus catalytic stages: a firstClaus catalytic stage includes first reheater 12, first catalyticreactor 14, and first condenser 16; and a second Claus catalytic stageincludes second reheater 22, second catalytic reactor 24, and secondcondenser 26. Referring to FIG. 2 and as described above, first gasstream 106 is fed to first reheater 12 of the first Claus catalyticstage to create first hot wet gas stream 212. First hot wet gas stream212 is fed to first catalytic reactor 14 to produce first catalyticoutlet stream 114. First catalytic outlet stream 114 is introduced tofirst condenser 16. First condenser 16 condenses elemental sulfurpresent in first catalytic outlet stream 114 to produce first sulfurstream 118 and second gas stream 116. Second gas stream 116 is fed tosecond reheater 22 to produce second hot wet gas stream 222. Second hotwet gas stream 222 is fed to second catalytic reactor 24 to producesecond catalytic outlet stream 124. Second catalytic outlet stream 124is introduced to second condenser 26. Second condenser 26 condenseselemental sulfur present in second catalytic outlet stream 124 toproduce second sulfur stream 128 and tail gas stream 136. Tail gasstream 136 contains those gases that did not condense in secondcondenser 26.

FIG. 3 depicts a system with three Claus catalytic stages: a first Clauscatalytic stage includes first reheater 12, first catalytic reactor 14,and first condenser 16; a second Claus catalytic stage includes secondreheater 22, second catalytic reactor 24, and second condenser 26; and athird Claus catalytic stage includes third reheater 32, third catalyticreactor 34, and third condenser 36. Referring to FIG. 3 and withreference to those elements described in connection with FIG. 2, in aprocess with three Claus catalytic stages, second condenser 26 producessecond sulfur stream 128 and third gas stream 126. Third gas stream 126contains those gases that did not condense in second sulfur condenser26. Third gas stream 126 is fed to third reheater 32 to produce thirdhot wet gas stream 232. Third hot wet gas stream 232 is fed to catalyticreactor 34 to produce third catalytic outlet stream 134. Third catalyticoutlet stream 134 is fed to third condenser 36. Third condenser 36condenses the elemental sulfur in third catalytic outlet stream 134 toproduce third sulfur stream 138 and tail gas stream 136. First hot wetgas stream 212 is at a higher temperature than second hot wet gas stream222 and second hot wet gas stream 222 is at a higher temperature thanthird hot wet gas stream 232. In the conventional Claus processesdescribed with reference to FIGS. 2 and 3, first gas stream 106, secondgas stream 116, and third gas stream 126 and first hot wet gas stream212, second hot wet gas stream 222, and third hot wet gas stream 232contain water vapor.

Advantageously, the present invention includes one or more adsorberssituated upstream of each of the Claus catalytic stages. The presentinvention can include one or fewer adsorbers upstream of each of thereheaters of the Claus catalytic stage.

According to an embodiment of the present invention, the first gasstream exiting the sulfur condenser is fed to an adsorber. The adsorbercan remove water vapor from the gas stream to produce a dry gas streamand a water stream. The adsorber can be any adsorption-dehydrationcolumn unit designed to remove water vapor from a wet gas stream. “Wetgas stream” as used herein, refers to a stream containing water vapor.

The adsorber can include any molecular sieve capable of selectivelyadsorbing water vapor from a wet gas stream while rejecting theremaining components in the gas phase due to their larger moleculardiameter. Molecular sieves operate by selectively adsorbing certaincomponents in a stream. Molecular sieves suitable for use in the presentinvention have a pore size measured in Angstroms (Å). Molecular sieveshave a crystal lattice that results in a well-ordered pore and cavitystructure. The effective channel diameter of the cages of the molecularsieve determines whether or not a molecule with a certain kineticdiameter can diffuse into the cage and be adsorbed. Any molecular sievethat has an adsorption affinity towards water and a channel diametersmall enough to exclude hydrogen sulfide, but large enough to allowwater to pass through can be used. Examples of molecular sieves that canbe used in the present invention include zeolite-3A. Zeolite-3A includesa potassium zeolite, an effective channel diameter (pore diameter) ofabout 3 Å, and a bulk density of 44 pounds/cubic foot. The kineticdiameter of water is about 2.6 Å. Zeolite-3A adsorbs water vapor andammonia. Hydrogen sulfide has a kinetic diameter of about 3.60 Å and isnot adsorbed by zeolite-3A. Molecular sieve 3A can include a binder. Incertain embodiments, the molecular sieve is produced by binding micronsized zeolite crystals together to form pellets, as is known in the art.The binder can include silica or other inert materials. Without beingbound by a particular theory, it is understood that because the binderis inert the performance of a molecular sieve is reduced proportionallyto the amount of binder. It is understood that a pellet design canminimize the amount of binder without foregoing strength of the pellet.For example, the equilibrium adsorption capacity of a molecular sievewith zeolite-3A pellets with binder is about 20 percent by weight (wt%), in other words, 20% of the total weight is water at equilibrium. Thebinder in molecular sieve 3A can be about 9 weight %.

The amount of adsorbed water vapor molecules for a given adsorbent is afunction of temperature and pressure. The amount of adsorbed waterincreases with increasing pressure and decreases with increasingtemperature. Referring to FIG. 11, the adsorption capacity for molecularsieve 3A at various temperatures (adsorption isotherms) is provided. Theadsorption capacity of molecular sieve 3A for water vapor at 100° C. issubstantially higher than the adsorption capacity for water at 200° C.The temperature in the adsorber is between 75° C. and 170° C.,alternately between 75° C. and 160° C., alternately between 75° C. and150° C., and alternately between 75° C. and 140° C. In at least oneembodiment, the temperature of the adsorber is between 75° C. and 150°C. The concentration of water in the dry gas stream is less than 1part-per-million (ppm), alternately less than 0.5 ppm, and alternatelyless than 0.1 ppm. In at least one embodiment, the concentration ofwater in the dry gas stream is less than 0.1 ppm.

The method for removal of sulfur including adsorbers can be understoodwith reference to FIGS. 1 and 4-9. FIG. 1 depicts a process with threeClaus catalytic stages and an adsorber upstream of each of the Clauscatalytic stages. Referring to FIG. 1 and with reference to thoseelements described in connection with FIGS. 2 and 3, first gas stream106 is fed to first adsorber 10. First adsorber 10 removes water vaporfrom first gas stream 106 to produce first dry gas stream 110. First drygas stream 110 is fed to first reheater 12 to produce hot dry gas stream112. Hot dry gas stream 112 is in the absence of all or substantiallyall water vapor. As used herein, “in the absence of substantially allwater vapor” or “in the absence of substantially all of the water vapor”means that less than 1.0 ppm water vapor is in hot dry gas stream 112.As used herein “in the absence of water vapor” or “in the absence of allwater vapor” means that the hot dry gas stream contains less than 0.1ppm. First hot dry gas stream 112 is fed to first catalytic reactor 14to produce first catalytic outlet stream 114. Second gas stream 116 isfed to second adsorber 20. Second adsorber 20 removes water vapor fromsecond gas stream 116 to produce second dry gas stream 120. Second drygas stream 120 is fed to second reheater 22 to produce second hot drygas stream 122. Second hot dry gas stream 122 is in the absence of allor substantially all water vapor. Second hot dry gas stream 122 is fedto second catalytic reactor 24 to produce second catalytic outlet stream124. Third gas stream 126 is fed to third adsorber 30. Third adsorber 30removes water vapor from third gas stream 126 to produce third dry gasstream 130. Third dry gas stream 130 is fed to third reheater 32 toproduce third hot dry gas stream 132. Hot dry gas stream 132 is in theabsence of all or substantially all water vapor. Third hot dry gasstream 132 is fed to third catalytic reactor 34 to produce thirdcatalytic outlet stream 134.

First dry gas stream 110, second dry gas stream 120 and third dry gasstream 130 are introduced to first reheater 12, second reheater 22, andthird reheater 32 respectively, to heat First dry gas stream 110, seconddry gas stream 120 and third dry gas stream 130 to the reactiontemperature in first catalytic reactor 14, second catalytic reactor 24,and third catalytic reactor 34, respectively.

With reference to FIGS. 1 and 3, one of skill in the art understandsthat the compositions of the streams can be the same with respect to thecomponents present, except for the presence of water vapor in certainstreams that are not treated by an adsorber. As an example, first hotdry gas stream 112 can contain the same components as first hot wet gasstream 212 except first hot wet gas stream 212 contains water vapor andfirst hot dry gas stream 112 is in the absence of water vapor.

The method for sulfur removal is in the absence of a condenser designedto condense water vapor from a gas stream. Advantageously, the use ofmolecular sieves for adsorption can remove all or substantially all ofthe water vapor from a wet gas stream. The use of molecular sievesadvantageously removes water to the ppm level as compared to a condenserwhich can remove water to the saturation point for the operatingtemperature and pressure. A condenser cannot be used to condense all orsubstantially all of the water vapor because the gas stream remainssaturated with water vapor due to thermodynamic equilibrium. In acondenser, for any given temperature, the liquid water will be atequilibrium with the vapor (the gas phase will be saturated watervapor), because of this a condenser cannot remove enough water for thepurposes of the present invention. In a molecular sieve, the adsorbentcan continue to adsorb water vapor and thus remove water until theadsorbent is saturated.

Following the final condenser in the system, the non-condensedcomponents form a tail gas stream. The tail gas stream can contain H₂S,SO₂, CO₂, H₂O, other gases, and combinations of the same. Tail gasstream 136 can be fed to an incinerator, can be vented to the atmosphereor an alternate process or alternate process unit for removingcontaminants from a stream.

A total conversion can be calculated from the total elemental sulfurrecovered and the amount of molecular sulfur in the acid gas stream.Total conversion can be between 99 wt % and 99.9 wt %.

As used herein, “adsorber” refers to a two bed system, where at anytime, one will be on an adsorption cycle and the second will be on aregeneration cycle. In a pressure swing adsorption (PSA) system, theregeneration cycle is driven by a decrease in the pressure in theregeneration bed compared to the pressure in the adsorption bed, causingcomponents to desorb. In a temperature swing adsorption (TSA) system,the regeneration cycle is driven by an increase in the temperature ofthe regeneration bed compared to the temperature in the adsorption bed,causing components to desorb. A combination of PSA and TSA can also beused. The pressure in the Claus process is not high enough for a PSAwithout expensive compression equipment. Therefore, the presentinvention is in the absence of a PSA process. A TSA system can be usedin the present invention. A TSA can be better understood with referenceto FIG. 10. As shown in FIG. 10, gas stream 106 is fed to adsorptioncolumn 10A to produce dry gas 110A. Adsorption column 10A is attemperature between 75° C. and 170° C., alternately between 100° C. and170° C., and alternately between 100° C. and 150° C. The residence timein adsorption column 10A can be greater than 2 hours and alternatelybetween 2 hours and 12 hours. Adsorption column 10A contains molecularsieve 3A. Water vapor in gas stream 106 is adsorbed by molecular sieve3A leaving behind dry gas 110A. A portion of dry gas 110A is fed toregeneration heater 10D and the remaining portion exits as dry gasstream 110. Regeneration heater 10D increases the temperature of dry gas110A to a temperature in the range between 175° C. and 260° C. toproduce heated gas 110D. Heated gas 110D is fed to regeneration column10B, which increases the temperature in regeneration column 10B. Theincreased temperature in regeneration column 10B causes water adsorbedon molecular sieve 3A in regeneration column 10B to desorb. The desorbedwater, in the form of water vapor, is carried from regeneration column10B as part of regenerated gas 110B. Regenerated gas 110B is cooled to atemperature below 100° C. to form cooled stream 110E. Cooled stream 110Eis fed to separator 10F, where liquid water is separated from the gasesin cooled stream 110E to produce water stream 110G and recycle gasstream 110F. Recycle gas stream 110F is mixed with gas stream 106 andfed to adsorption column 10A. In certain embodiments, an adsorber, suchas a TSA can include a buffer tank on the inlet stream.

Through valves and other piping components, the adsorption column can beswitched to the regeneration column as needed.

EXAMPLES

The process of the present invention can be readily understood byExamples. The following examples were simulated using a HYSYS processsimulator to simulate the method of the present invention. Thesimulations were based on FIGS. 1-9 as indicated below and describedabove. In all of the Examples, acid gas stream 100 was simulated at atemperature of 30.0° C. and a flow rate of 110.0 kgmol/hr (3848.0kg/hr). Acid gas stream 100 had a composition of 100.0 kmol/hr ofhydrogen sulfide and 10.0 kmol/hr of carbon dioxide. The flow rate ofair feed 102 was automatically adjusted by the simulation so combustionfurnace 3 had a simulated burn of one-third (⅓) of the hydrogen sulfidepresent in acid gas stream 100 with air from air feed 102 to produceSO₂. Combustion furnace 3 operated in a range 979° C.-1050° C. Gibbsenergy minimization was used to simulate the Claus thermal reaction,reaction (3), in combustion furnace 3 and the Claus catalytic reaction,reaction (1), in the catalytic reactors 14, 24, and as applicable, 34.As applicable, adsorbers 10, 20, and 30 were modeled for 100% watervapor removal from gas streams 106, 116, and 126. Water vapor removal of100% is appropriate given that molecular sieve 3A can remove water vaporto the ppm level.

Example 1

Example 1, a comparative example, was simulated based on FIG. 3, aprocess flow diagram of a conventional Claus process, including threecatalytic reactors: first catalytic reactor 14, second catalytic reactor24, and third catalytic reactor 34. First reheater 12 increased thetemperature of first gas stream 106 to a temperature of 235° C. toproduce first hot wet gas stream 212. Second reheater 22 increased thetemperature of second gas stream 116 to a temperature of 215° C. toproduce second hot wet gas stream 222. Third reheater 32 increased thetemperature of third gas stream 126 to a temperature of 205° C. toproduce third hot wet gas stream 232. The total sulfur recovered was3157.8 kg/hr for a total conversion of 98.5 weight percent (wt %)sulfur.

TABLE 1 Stream properties and results in Example 1 Stream No. 103 105106 114 116 124 126 134 136 Temperature 979.0 315.0 190.0 309.6 176.0236.3 149.0 209.8 132.0 Flow rate, 342.4 342.4 309.0 304.5 301.1 299.9299.1 298.8 298.6 kgmol/hr Flow rate, 10720.0 1072.0 8558.0 8558.07802.0 7802.0 7603.0 7603.0 7560.0 kg/hr Component flow rate, kmol/hrH₂S 21.7612 21.7612 21.7612 6.0443 6.0443 1.9240 1.9240 1.0185 1.0185SO₂ 10.8806 10.8806 10.8806 3.0221 3.0221 0.9620 0.9620 0.5092 0.5092H₂O 78.2 78.2 78.2 94.0 94.0 98.1 98.1 99.0 99.0 CO₂ 10.0 10.0 10.0 10.010.0 10.0 10.0 10.0 10.0 N₂ 188.1 188.1 188.1 188.1 188.1 188.1 188.1188.1 188.1 S₂ 33.0752 33.0752 0.0000 0.0741 0.0 0.0027 0.000 0.00050.000 S₃ 0.0 0.0000 0.0000 0.0078 0.0 0.0002 0.000 0.0000 0.000 S₄0.3829 0.3829 0.0000 0.0052 0.0 0.0002 0.000 0.0000 0.000 S₅ 0.01460.0145 0.0000 0.0752 0.0 0.0098 0.000 0.0021 0.000 S₆ 0.0001 0.00010.0000 0.9895 0.0 0.1980 0.000 0.0457 0.000 S₇ 0.0000 0.0000 0.00000.5772 0.0 0.1081 0.000 0.0199 0.000 S₈ 0.0000 0.0000 0.0000 1.6286 0.00.5269 0.000 0.1166 0.000 Total sulfur, 2160.0 756.0 198.2 43.6 kg/hrConversion 67.4 90.9 97.1 98.5 of H₂S, wt %

Example 1-1

Example 1-1 is a HYSYS simulation according to FIG. 4, a system havingone adsorber immediately downstream of sulfur condenser 6. Firstadsorber 10 removed 78.2 kgmol/hr (1409.0 kg/hr) of water from first gasstream 106. First reheater 12 increased the temperature of first dry gasstream 110 to a temperature of 235° C. to produce first hot dry gasstream 112. Second reheater 22 increased the temperature of second gasstream 116 to a temperature of 215° C. to produce first hot wet gasstream 222. Third reheater 32 increased the temperature of third gasstream 126 to a temperature of 205° C. to produce second hot wet gasstream 232. The total sulfur recovered was 3193.0 kg/hr for a totalconversion of sulfur of 99.6 wt %.

TABLE 2 Stream Properties and results in Example 1-1 Stream No. 103 105106 110 114 116 124 126 134 136 Temperature 979.0 315.0 100.0 352.1176.0 233.6 149.0 207.2 132.0 Flow rate, 342.4 342.4 309.0 230.7 225.6221.4 220.7 220.1 220.1 220.0 kgmol/hr Flow rate, 10720.0 1072.0 8558.07148.0 7148.0 6252.0 6252.0 6252.0 6129.0 6115.0 kg/hr Component flowrate, kmol/hr H₂S 21.7612 21.7612 21.7612 21.7612 3.1313 3.1313 0.58530.5853 0.2852 0.2852 SO₂ 10.8806 10.8806 10.8806 10.8806 1.5657 1.56570.2957 0.2957 0.1526 0.1526 H₂O 78.2 78.2 78.2 0.0 18.6 18.6 21.2 21.221.5 21.5 CO₂ 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 N₂ 188.1188.1 188.1 188.1 188.1 188.1 188.1 188.1 188.1 S₂ 33.0752 33.07520.0000 0.2448 0.0 0.0017 0.000 0.0003 0.000 S₃ 0.0 0.0000 0.0000 0.02660.0 0.0001 0.000 0.0000 0.000 S₄ 0.3829 0.3829 0.0000 0.0169 0.0 0.00010.000 0.0000 0.000 S₅ 0.0146 0.0145 0.0000 0.1259 0.0 0.0061 0.0000.0009 0.000 S₆ 0.0001 0.0001 0.0000 1.3214 0.0 0.1236 0.000 0.01720.000 S₇ 0.0000 0.0000 0.0000 0.7929 0.0 0.0630 0.000 0.0068 0.000 S₈0.0000 0.0000 0.0000 1.6503 0.0 0.3252 0.000 0.0368 0.000 Total sulfur,2160.0 896.1 122.5 14.4 kg/hr Conversion 67.4 95.3 99.1 99.6 of H₂S, wt%

Example 1-2 is a HYSYS simulation according to FIG. 5, a system havingtwo adsorbers. First adsorber 10 removed 78.2 kgmol/hr (1409.0 kg/hr) ofwater from first gas stream 106. First reheater 12 increased thetemperature of first dry gas stream 110 to a temperature of 235° C. toproduce first hot dry gas stream 112. Second adsorber 20 removed 18.6kgmol/hr (335.6 kg/hr) of water from second gas stream 116. Secondreheater 22 increased the temperature of second dry gas stream 120 to atemperature of 215° C. to produce second hot dry gas stream 122. Thirdreheater 32 increased the temperature of third gas stream 126 to atemperature of 205° C. to produce first hot wet gas stream 232. Thetotal sulfur recovered was 3203.6.0 kg/hr for a total conversion ofsulfur of 99.9 wt %.

TABLE 3 Stream properties in Example 1-2 Stream No. 103 105 106 110 114116 120 124 126 134 136 Temperature 979.0 315.0 100.0 352.1 100.0 238.9149.0 205.9 132.0 Flow rate, 342.4 342.4 309.0 230.7 225.6 221.4 202.8201.9 201.3 201.3 220.0 kgmol/hr Flow rate, 10720.0 1072.0 8558.0 7148.07148.0 6252.0 5916.0 5916.0 5774.0 5774.0 6115.0 kg/hr Component flowrate, kmol/hr H₂S 21.7612 21.7612 21.7612 21.7612 3.1313 3.1313 3.13130.1716 0.1716 0.0649 0.0649 SO₂ 10.8806 10.8806 10.8806 10.8806 1.56571.5657 1.5657 0.0858 0.0858 0.0325 0.0325 H₂O 78.2 78.2 78.2 0.0 18.618.6 0.0000 3.0 3.0 3.0 3.0 CO₂ 10.0 10.0 10.0 10.0 10.0 0.0000 10.010.0 10.0 10.0 N₂ 188.1 188.1 188.1 188.1 188.1 0.0000 188.1 188.1 188.1188.1 S₂ 33.0752 33.0752 0.0000 0.0000 0.2448 0.0 0.0000 0.0021 0.0000.0002 0.000 S₃ 0.0 0.0000 0.0000 0.0000 0.0266 0.0 0.0000 0.0002 0.0000.0000 0.000 S₄ 0.3829 0.3829 0.0000 0.0000 0.0169 0.0 0.0000 0.00010.000 0.0000 0.000 S₅ 0.0146 0.0145 0.0000 0.0000 0.1259 0.0 0.00000.0072 0.000 0.0004 0.000 S₆ 0.0001 0.0001 0.0000 0.0000 1.3214 0.00.0000 0.1437 0.000 0.0074 0.000 S₇ 0.0000 0.0000 0.0000 0.0000 0.79290.0 0.0000 0.0752 0.000 0.0025 0.000 S₈ 0.0000 0.0000 0.0000 0.00001.6503 0.0 0.0000 0.3761 0.000 0.0121 0.000 Total sulfur, 2160.0 896.1142.4 5.1 kg/hr Conversion 67.4 95.3 99.7 99.9 of H₂S, wt %

Example 1-3 is a HYSYS simulation according to FIG. 1, a system havingthree adsorbers. Adsorber 10 removed 78.2 kgmol/hr (1409.0 kg/hr) ofwater from first gas stream 106. First reheater 12 increased thetemperature of first dry gas stream 110 to a temperature of 235° C. toproduce first hot dry gas stream 112. Second adsorber 20 removed 18.6kgmol/hr (335.6 kg/hr) of water from second gas stream 116. Secondreheater 22 increased the temperature of second dry gas stream 120 to atemperature of 215° C. to produce second hot dry gas stream 122. Thirdadsorber 30 produced 3.0 kgmol/hr (53.3 kg/hr) of water from third gasstream 126. Third reheater 32 increased the temperature of third gasstream 126 to a temperature of 205° C. to produce third hot dry gasstream 132. The total sulfur recovered was 3206.3.0 kg/hr for a totalconversion of sulfur of 100.0 wt %.

TABLE 4 Stream properties in Example 1-3 Stream No. 103 105 106 110 114116 Temperature 979.0 315.0 100.0 100.0 352.1 100.0 Flow rate, 342.4342.4 309.0 230.7 225.6 221.4 kgmol/hr Flow rate, 10720.0 1072.0 8558.07148.0 7148.0 6252.0 kg/hr Component flow rate, kmol/hr H₂S 21.761221.7612 21.7612 21.7612 3.1313 3.1313 SO₂ 10.8806 10.8806 10.880610.8806 1.5657 1.5657 H₂O 78.2 78.2 78.2 0.0 18.6 18.6 CO₂ 10.0 10.010.0 10.0 10.0 N₂ 188.1 188.1 188.1 188.1 188.1 S₂ 33.0752 33.07520.0000 0.2448 0.0 S₃ 0.0 0.0000 0.0000 0.0266 0.0 S₄ 0.3829 0.38290.0000 0.0169 0.0 S₅ 0.0146 0.0145 0.0000 0.1259 0.0 S₆ 0.0001 0.00010.0000 1.3214 0.0 S₇ 0.0000 0.000 0.0000 0.7929 0.0 S₈ 1.6503 0.0 Totalsulfur, 2160.0 896.1 kg/hr Conversion 67.4 95.3 of H₂S, wt % Stream No.120 124 126 130 134 136 Temperature 100.0 238.9 100.0 100.0 206.3 132.0Flow rate, 202.8 201.9 201.3 198.4 198.3 198.3 kgmol/hr Flow rate,5916.0 5916.0 5774.0 5721.0 5721.0 5713.0 kg/hr Component flow rate,kmol/hr H₂S 3.1313 0.1716 0.1716 0.1716 0.0097 0.0649 SO₂ 1.5657 0.08580.0858 0.0858 0.0049 0.0049 H₂O 0.0000 3.0 3.0 0.2 0.2 CO₂ 0.0000 10.010.0 10.0 10.0 N₂ 0.0000 188.1 188.1 188.1 188.1 S₂ 0.0000 0.0021 0.0000.0002 0.000 S₃ 0.0000 0.0002 0.000 0.0000 0.000 S₄ 0.0000 0.0001 0.0000.0000 0.000 S₅ 0.0000 0.0072 0.000 0.0005 0.000 S₆ 0.0000 0.1437 0.0000.0101 0.000 S₇ 0.0000 0.0752 0.000 0.0037 0.000 S₈ 0.0000 0.3761 0.0000.0191 0.000 Total sulfur, 142.4 7.8 kg/hr Conversion 99.7 100.0 of H₂S,wt %

Example 1-4 is a HYSYS simulation according to FIG. 6 having oneadsorber upstream of the final Claus catalytic stage. First reheater 12increased the temperature of first gas stream 106 to a temperature of235° C. to produce first hot wet gas stream 212. Second reheater 22increased the temperature of second gas stream 116 to a temperature of215° C. to produce second hot wet gas stream 222. First adsorber 10removed 98.1 kgmol/hr (1767.0 kg/hr) of water from third gas stream 126.Third reheater 32 increased the temperature of first dry gas stream 110to a temperature of 205° C. to produce first hot dry gas stream 132. Thetotal sulfur recovered was 3202.6 kg/hr for a total conversion of 99.9wt %.

TABLE 5 Stream properties in Example 1-4 Stream No. 103 105 106 114 116124 126 130 134 136 Temperature 979.0 315.0 190.0 309.6 176.0 236.3100.0 100.0 220.2 132.0 Flow rate, 342.4 342.4 309.0 304.5 301.1 299.9299.1 201.0 200.4 298.6 kgmol/hr Flow rate, 10720.0 1072.0 8558.0 8558.07802.0 7802.0 7603.0 5837.0 5837.0 7560.0 kg/hr Component flow rate,kmol/hr H₂S 21.7612 21.7612 21.7612 6.0443 6.0443 1.9240 1.9240 1.92400.0866 1.0185 SO₂ 10.8806 10.8806 10.8806 3.0221 3.0221 0.9620 0.96200.9620 0.0433 0.5092 H₂O 78.2 78.2 78.2 94.0 94.0 98.1 98.1 0.0000 1.899.0 CO₂ 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 N₂ 188.1 188.1188.1 188.1 188.1 188.1 188.1 188.1 188.1 S₂ 33.0752 33.0752 0.00000.0741 0.0 0.0027 0.000 0.0007 0.000 S₃ 0.0 0.0000 0.0000 0.0078 0.00.0002 0.000 0.0001 0.000 S₄ 0.3829 0.3829 0.0000 0.0052 0.0 0.00020.000 0.0000 0.000 S₅ 0.0146 0.0145 0.0000 0.0752 0.0 0.0098 0.0000.0037 0.000 S₆ 0.0001 0.0001 0.0000 0.9895 0.0 0.1980 0.000 0.08240.000 S₇ 0.0000 0.000 0.0000 0.5772 0.0 0.1081 0.000 0.0412 0.000 S₈1.6286 0.0 0.5269 0.000 0.2441 0.000 Total sulfur, 2160.0 756.0 198.288.4 kg/hr Conversion 67.4 90.9 97.1 99.9 of H₂S, wt %

The results of Examples 1 through 1-4 indicate that the adsorbersincrease the conversion of sulfur in the catalytic reactors. Table 6 isa comparison of the results. Having even one adsorber to remove waterfrom the process increases the conversion by at least 1% over the systemin Example 1 that had no adsorbers.

TABLE 6 Comparison of sulfur conversion Conversion % # of CombustionCatalytic Catalytic Catalytic Kg sulfur/100 mol Ex. Adsorbers FIG. #Furnace Reactor Reactor Reactor Overall H₂S 1 None 3 67.4 90.9 97.1 98.598.5 3158 1-1 One 4 67.4 95.3 99.1 99.6 99.6 3193 1-2 Two 5 67.4 95.399.7 99.9 99.9 3203 1-3 Three 1 67.4 95.3 99.7 100.0 100.0 3206 1-4 One6 67.4 90.9 97.1 99.9 99.9 3203

Example 2

Example 2, a comparative example, is a HYSYS simulation according toFIG. 2, a process flow diagram of a conventional Claus process,including two catalytic reactors: first catalytic reactor 14 and secondcatalytic reactor 24. First reheater 12 increased the temperature offirst gas stream 106 to a temperature of 235° C. to produce first hotwet gas stream 212. Second reheater 22 increased the temperature ofsecond gas stream 116 to a temperature of 205° C. to produce second hotwet gas stream 222. The total sulfur recovered was 3157.8 kg/hr for atotal conversion of 97.5 wt %.

TABLE 7 Stream properties and results for Example 2 Stream No. 103 105106 114 116 124 136 Temperature 979.0 315.0 190.0 309.6 176.0 227.7132.0 Flow rate, 342.4 342.4 309.0 304.5 301.1 299.8 298.9 kgmol/hr Flowrate, 10720.0 1072.0 8558.0 8558.0 7802.0 7802.0 7592.0 kg/hr Componentflow rate, kmol/hr H₂S 21.7612 21.7612 21.7612 6.0443 6.0443 1.69181.6918 O₂ SO₂ 10.8806 10.8806 10.8806 3.0221 3.0221 0.8459 0.8459 H₂O78.2 78.2 78.2 94.0 94.0 98.3 98.3 CO₂ 10.0 10.0 10.0 10.0 10.0 10.010.0 N₂ 188.1 188.1 188.1 188.1 188.1 188.1 188.1 S₂ 33.0752 33.07520.0000 0.0741 0.0 0.0018 0.000 S₃ 0.0 0.0000 0.0000 0.0078 0.0 0.00020.000 S₄ 0.3829 0.3829 0.0000 0.0052 0.0 0.0001 0.000 S₅ 0.0146 0.01450.0000 0.0752 0.0 0.0087 0.000 S₆ 0.0001 0.0001 0.0000 0.9895 0.0 0.19170.000 S₇ 0.0000 0.000 0.0000 0.5772 0.0 0.1011 0.000 S₈ 1.6286 0.00.5782 0.000 Total sulfur, 2160.0 756.0 209.3 kg/hr Conversion 67.4 90.997.5 of H₂S,

Example 2-1 is a HYSYS simulation according to FIG. 7 having oneadsorber upstream of the first Claus catalytic stage. First adsorber 10removed 78.2 kgmol/hr (1409.0 kg/hr) of water from first gas stream 106.First reheater 12 increased the temperature of first dry gas stream 110to a temperature of 235° C. to produce first hot dry gas stream 112.Second reheater 22 increased the temperature of second gas stream 116 toa temperature of 205° C. to produce first hot wet gas stream 222. Thetotal sulfur recovered was 3281.3 kg/hr for a total conversion of 99.2wt %.

TABLE 8 Stream properties and results for Example 2-1 Stream No. 103 105106 110 114 116 124 136 Temperature 979.0 315.0 100.0 352.1 176.0 224.6132.0 (° C.) Flow rate, 342.4 342.4 309.0 230.7 225.6 221.4 220.1 220.1kgmol/hr Flow rate, 10720.0 1072.0 8558.0 7148.0 7148.0 6252.0 6252.06126.0 kg/hr Component flow rate, kmol/hr H₂S 21.7612 21.7612 21.761221.7612 3.1313 3.1313 0.5072 0.5072 SO₂ 10.8806 10.8806 10.8806 10.88061.5657 1.5657 0.2536 0.2536 H₂O 78.2 78.2 78.2 0.0 18.6 18.6 21.3 21.3CO₂ 10.0 10.0 10.0 10.0 10.0 10.0 10.0 N₂ 188.1 188.1 188.1 188.1 188.1188.1 188.1 S₂ 33.0752 33.0752 0.0000 0.2448 0.0 0.0011 0.000 S₃ 0.00.0000 0.0000 0.0266 0.0 0.0001 0.000 S₄ 0.3829 0.3829 0.0000 0.0169 0.00.0001 0.000 S₅ 0.0146 0.0145 0.0000 0.1259 0.0 0.0052 0.000 S₆ 0.00010.0001 0.0000 1.3214 0.0 0.1163 0.000 S₇ 0.0000 0.000 0.0000 0.7929 0.00.0600 0.000 S₈ 1.6503 0.0 0.3487 0.000 Total sulfur, 2160.0 896.1 225.2kg/hr Conversion 67.4 95.3 99.2 H₂S, wt %

Example 2-2 is a HYSYS simulation according to FIG. 8 having twoadsorbers. First adsorber 10 removed 78.2 kgmol/hr (1409.0 kg/hr) ofwater from first gas stream 106. First reheater 12 increased thetemperature of first dry gas stream 110 to a temperature of 235° C. toproduce first hot dry gas stream 112. Second adsorber 20 removed 18.6kgmol/hr (335.6 kg/hr) of water from second gas stream 116. Secondreheater 22 increased the temperature of second dry gas stream 120 to atemperature of 205° C. to produce second hot dry gas stream 122. Thetotal sulfur recovered was 3199.6 kg/hr for a total conversion of 99.8wt %.

TABLE 9 Stream properties and results for Example 2-2 Stream No. 103 105106 110 114 116 120 124 136 Temperature 979.0 315.0 100.0 352.1 100.0229.3 132.0 Flow rate, 342.4 342.4 309.0 230.7 225.6 221.4 202.8 201.9201.3 kgmol/hr Flow rate, 10720.0 1072.0 8558.0 7148.0 7148.0 6252.05916.0 5916.0 5773.0 kg/hr Component flow rate, kmol/hr H₂S 21.761221.7612 21.7612 21.7612 3.1313 3.1313 3.1313 0.1483 0.1483 SO₂ 10.880610.8806 10.8806 10.8806 1.5657 1.5657 1.5657 0.0742 0.0742 H₂O 78.2 78.278.2 0.0 18.6 18.6 0.0000 3.0 3.0 CO₂ 10.0 10.0 10.0 10.0 10.0 0.000010.0 10.0 N₂ 188.1 188.1 188.1 188.1 188.1 0.0000 188.1 188.1 S₂ 33.075233.0752 0.0000 0.2448 0.0 0.0000 0.0013 0.000 S₃ 0.0 0.0000 0.00000.0266 0.0 0.0000 0.0001 0.000 S₄ 0.3829 0.3829 0.0000 0.0169 0.0 0.00000.0001 0.000 S₅ 0.0146 0.0145 0.0000 0.1259 0.0 0.0000 0.0061 0.000 S₆0.0001 0.0001 0.0000 1.3214 0.0 0.0000 0.1351 0.000 S₇ 0.0000 0.0000.0000 0.7929 0.0 0.0000 0.0701 0.000 S₈ 1.6503 0.0 0.0000 0.3943 0.000Total sulfur, 2160.0 896.1 143.5 kg/hr Conversion 67.4 95.3 99.8 of H₂S,

Example 2-3 is a HYSYS simulation according to FIG. 9 having oneadsorber upstream of the final Claus catalytic stage. First reheater 12increased the temperature of first gas stream 106 to a temperature of235° C. to produce hot wet gas stream 212. Adsorber 10 removed 94.0kgmol/hr (1693.0 kg/hr) of water from second gas stream 116. Secondreheater 22 increased the temperature of dry gas stream 110 to atemperature of 205° C. to produce hot dry gas stream 122. The totalsulfur recovered was 3190.2 kg/hr for a total conversion of 99.5 wt %.

TABLE 10 Stream properties and results for Example 2-3 103 105 106 114116 110 124 136 Temperature 979.0 315.0 190.0 309.6 100.0 100.0 249.8132.0 Flow rate, 342.4 342.4 309.0 304.5 301.1 94.0 205.5 201.3 kgmol/hrFlow rate, 10720.0 1072.0 8558.0 8558.0 7802.0 1693.0 6109.0 5773.0kg/hr Component flow rate, kmol/hr H₂S 21.7612 21.7612 21.7612 6.04436.0443 6.0443 0.3429 0.3429 SO₂ 10.8806 10.8806 10.8806 3.0221 3.02213.0221 0.1714 0.1714 H₂O 78.2 78.2 78.2 94.0 94.0 0.0000 5.7 5.7 CO₂10.0 10.0 10.0 10.0 10.0 0.000 10.0 10.0 N₂ 188.1 188.1 188.1 188.1188.1 0.000 188.1 188.1 S₂ 33.0752 33.0752 0.0000 0.0741 0.0 0.0000.0041 0.000 S₃ 0.0 0.0000 0.0000 0.0078 0.0 0.000 0.0004 0.000 S₄0.3829 0.3829 0.0000 0.0052 0.0 0.000 0.0003 0.000 S₅ 0.0146 0.01450.0000 0.0752 0.0 0.000 0.0136 0.000 S₆ 0.0001 0.0001 0.0000 0.9895 0.00.000 0.2677 0.000 S₇ 0.0000 0.000 0.0000 0.5772 0.0 0.000 0.1513 0.000S₈ 1.6286 0.0 0.000 0.7261 0.000 Total sulfur, 2160.0 756.0 274.2 kg/hrConversion 67.4 90.9 99.5 of H₂S,

The results of Examples 2 through 2-3 indicate that the adsorbersincrease the conversion of sulfur in the catalytic reactors. Table 11 isa comparison of the results. In a Claus process having two Clauscatalytic stages, even one adsorber can increase the sulfur recovery, sothat the Claus process can achieve greater than 99 wt % removal ofsulfur.

TABLE 11 Comparison of sulfur conversion Conversion % # of CombustionCatalytic Catalytic Kg sulfur/100 mol Ex. Adsorbers FIG. # FurnaceReactor Reactor Overall H₂S 2 None 7 67.4 90.9 97.5 97.5 3125 2-1 One 867.4 95.3 99.2 99.2 3182 2-2 Two 9 67.4 95.3 99.8 99.8 3199 2-3 One 1067.4 90.9 99.5 99.5 3190

If the minimum requirement for hydrogen sulfide conversion is 99.5 wt %,all of the Examples using adsorbers achieve the minimum requirementexcept the two Claus catalytic stage with only one adsorber upstream ofthe first Claus catalytic stage. The Examples illustrate that theremoval of water by adsorbers in addition to the removal of sulfur inthe condensers increases the conversion in the Claus catalytic reactors.

Although embodiments have been described in detail, it should beunderstood that various changes, substitutions, and alterations can bemade without departing from the principle and scope of the invention.Accordingly, the scope should be determined by the following claims andtheir appropriate legal equivalents.

The singular forms “a,” “an,” and “the” include plural referents, unlessthe context clearly dictates otherwise.

“Optional” or “optionally” means that the subsequently described eventor circumstances can or may not occur. The description includesinstances where the event or circumstance occurs and instances where itdoes not occur.

Ranges may be expressed throughout as from about one particular value toabout another particular value. When such a range is expressed, it is tobe understood that another embodiment is from the one particular valueto the other particular value, along with all combinations within saidrange.

As used throughout and in the appended claims, the words “comprise,”“has,” and “include” and all grammatical variations thereof are eachintended to have an open, non-limiting meaning that does not excludeadditional elements or steps.

As used throughout, terms such as “first” and “second” are assignedbased on the position of the unit in the flow path and are merelyintended to differentiate between two or more of the same units in thesystem. It is to be understood that the words “first” and “second” serveno other purpose and are not part of the name or description of thecomponent. Furthermore, it is to be understood that that the mere use ofthe term “first” and “second” does not require that there be any “third”component, although that possibility is contemplated under the scope.

What is claimed is:
 1. A method to recover sulfur from hydrogen sulfidein an acid gas stream, the method comprising the steps of: feeding theacid gas stream to a combustion furnace to produce a furnace outletstream, the combustion furnace configured to convert the hydrogensulfide to elemental sulfur, wherein the furnace outlet stream compriseselemental sulfur, hydrogen sulfide, sulfur dioxide, and water vapor;introducing the furnace outlet stream to a waste heat boiler to producea cooled furnace outlet stream, the waste heat boiler configured toreduce a temperature of the furnace outlet stream; condensing the cooledfurnace stream in a sulfur condenser to produce a liquid sulfur streamand a gas stream, the sulfur condenser configured to reduce atemperature of the cooled furnace stream to a temperature below a dewpoint of elemental sulfur and above a dew point of water; and feedingthe gas stream to an adsorber to produce a dry gas stream and a waterstream, wherein the adsorber comprises a molecular sieve, wherein thedry gas stream is in the absence of water vapor, wherein the dry gasstream comprises hydrogen sulfide and sulfur dioxide.
 2. The method ofclaim 1, further comprising the steps of: introducing the dry gas streamto a first Claus catalytic stage; producing a second gas stream and afirst sulfur stream in the first Claus catalytic stage, wherein thefirst sulfur stream comprises liquid sulfur, wherein the second gasstream comprises hydrogen sulfide, sulfur dioxide, and water vapor;introducing the second gas stream to a second Claus catalytic stage;producing a third gas stream and a second sulfur stream in the secondClaus catalytic stage, wherein the second sulfur stream comprises liquidsulfur, wherein the third gas stream comprises hydrogen sulfide, sulfurdioxide, and water vapor; introducing the third gas stream to a thirdClaus catalytic stage; and producing a tail gas stream and a thirdsulfur stream in the third Claus catalytic stage, wherein the thirdsulfur stream comprises liquid sulfur, wherein the tail gas streamcomprises hydrogen sulfide, sulfur dioxide, and water vapor.
 3. Themethod of claim 1, further comprising the steps of: introducing the drygas stream to a first Claus catalytic stage; producing a second gasstream and a first sulfur stream in the first Claus catalytic stage,wherein the first sulfur stream comprises liquid sulfur, wherein thesecond gas stream comprises hydrogen sulfide, sulfur dioxide, and watervapor; introducing the second gas stream to a second Claus catalyticstage; and producing a tail gas stream and a second sulfur stream in thesecond Claus catalytic stage, wherein the second sulfur stream comprisesliquid sulfur, wherein the tail gas stream comprises hydrogen sulfide,sulfur dioxide, and water vapor.
 4. The method of claim 1, furthercomprising the steps of: introducing the dry gas stream to a first Clauscatalytic stage; producing a second gas stream and a first sulfur streamin the first Claus catalytic stage, wherein the first sulfur streamcomprises liquid sulfur, wherein the second gas stream compriseshydrogen sulfide, sulfur dioxide, and water vapor; introducing thesecond gas stream to a second adsorber, wherein the second adsorbercomprises a molecular sieve; producing a second dry gas stream and asecond water stream in the second adsorber, wherein the second dry gasstream is in the absence of water vapor, wherein the second dry gasstream comprises hydrogen sulfide and sulfur dioxide; introducing thesecond dry gas stream to a second Claus catalytic stage; producing athird gas stream and a second sulfur stream in the second Clauscatalytic stage, wherein the second sulfur stream comprises liquidsulfur, wherein the third gas stream comprises hydrogen sulfide, sulfurdioxide, and water vapor; introducing the third gas stream to a thirdClaus catalytic stage; and producing a tail gas stream and a thirdsulfur stream in the third Claus catalytic stage, wherein the thirdsulfur stream comprises liquid sulfur, wherein the tail gas streamcomprises hydrogen sulfide, sulfur dioxide, and water vapor.
 5. Themethod of claim 1, further comprising the steps of: introducing the drygas stream to a first Claus catalytic stage; producing a second gasstream and a first sulfur stream in the first Claus catalytic stage,wherein the first sulfur stream comprises liquid sulfur, wherein thesecond gas stream comprises hydrogen sulfide, sulfur dioxide, and watervapor; introducing the second gas stream to a second adsorber, whereinthe second adsorber comprises a molecular sieve; producing a second drygas stream and a second water stream in the second adsorber, wherein thesecond dry gas stream is in the absence of water vapor, wherein thesecond dry gas stream comprises hydrogen sulfide and sulfur dioxide;introducing the second dry gas stream to a second Claus catalytic stage;producing a tail gas stream and a second sulfur stream in the secondClaus catalytic stage, wherein the second sulfur stream comprises liquidsulfur, wherein the tail gas stream comprises hydrogen sulfide, sulfurdioxide, and water vapor.
 6. The method of claim 1, wherein themolecular sieve is molecular sieve 3A.
 7. A method to recover sulfurfrom hydrogen sulfide in an acid gas stream, the method comprising thesteps of: feeding the acid gas stream to a combustion furnace to producea furnace outlet stream, the combustion furnace configured to convertthe hydrogen sulfide to elemental sulfur, wherein the furnace outletstream comprises elemental sulfur, hydrogen sulfide, sulfur dioxide, andwater vapor; introducing the furnace outlet stream to a waste heatboiler to produce a cooled furnace outlet stream, the waste heat boilerconfigured to reduce a temperature of the furnace outlet stream;condensing the cooled furnace stream in a sulfur condenser to produce aliquid sulfur stream and a first gas stream, the sulfur condenserconfigured to reduce a temperature of the cooled furnace stream to atemperature below a dew point of elemental sulfur and above a dew pointof water; and introducing the first gas stream to a first Clauscatalytic stage; producing a second gas stream and a first sulfur streamin the first Claus catalytic stage, wherein the first sulfur streamcomprises liquid sulfur, wherein the second gas stream compriseshydrogen sulfide, sulfur dioxide, and water vapor; introducing thesecond gas stream to a second Claus catalytic stage; producing a thirdgas stream and a second sulfur stream in the second Claus catalyticstage, wherein the second sulfur stream comprises liquid sulfur, whereinthe third gas stream comprises hydrogen sulfide, sulfur dioxide, andwater vapor; feeding the third gas stream to an adsorber to produce adry gas stream and a water stream, wherein the adsorber comprises amolecular sieve, wherein the dry gas stream is in the absence of watervapor, wherein the dry gas stream comprises hydrogen sulfide and sulfurdioxide introducing the dry gas stream to a third Claus catalytic stage;and producing a tail gas stream and a third sulfur stream in the thirdClaus catalytic stage, wherein the third sulfur stream comprises liquidsulfur, wherein the tail gas stream comprises hydrogen sulfide, sulfurdioxide, and water vapor.
 8. The method of claim 7, wherein themolecular sieve is molecular sieve 3A.
 9. A method to recover sulfurfrom hydrogen sulfide in an acid gas stream, the method comprising thesteps of: feeding the acid gas stream to a combustion furnace to producea furnace outlet stream, the combustion furnace configured to convertthe hydrogen sulfide to elemental sulfur, wherein the furnace outletstream comprises elemental sulfur, hydrogen sulfide, sulfur dioxide, andwater vapor; introducing the furnace outlet stream to a waste heatboiler to produce a cooled furnace outlet stream, the waste heat boilerconfigured to reduce a temperature of the furnace outlet stream;condensing the cooled furnace stream in a sulfur condenser to produce aliquid sulfur stream and a first gas stream, the sulfur condenserconfigured to reduce a temperature of the cooled furnace stream to atemperature below a dew point of elemental sulfur and above a dew pointof water; and introducing the first gas stream to a first Clauscatalytic stage; producing a second gas stream and a first sulfur streamin the first Claus catalytic stage, wherein the first sulfur streamcomprises liquid sulfur, wherein the second gas stream compriseshydrogen sulfide, sulfur dioxide, and water vapor; feeding the secondgas stream to an adsorber to produce a dry gas stream and a waterstream, wherein the adsorber comprises a molecular sieve, wherein thedry gas stream is in the absence of water vapor, wherein the dry gasstream comprises hydrogen sulfide and sulfur dioxide introducing the drygas stream to a second Claus catalytic stage; and producing a tail gasstream and a second sulfur stream in the second Claus catalytic stage,wherein the second sulfur stream comprises liquid sulfur, wherein thetail gas stream comprises hydrogen sulfide, sulfur dioxide, and watervapor.
 10. The method of claim 9, wherein the molecular sieve ismolecular sieve 3A.
 11. A system to recover sulfur from hydrogen sulfidein an acid gas stream, the system comprising: a combustion furnace, thecombustion furnace configured to convert the hydrogen sulfide toelemental sulfur to produce a furnace outlet stream, wherein the furnaceoutlet stream comprises elemental sulfur, hydrogen sulfide, sulfurdioxide, and water vapor; a waste heat boiler fluidly connected to thecombustion furnace, the waste heat boiler configured to remove heat fromthe furnace outlet stream to produce a cooled furnace stream; a sulfurcondenser fluidly connected to the waste heat boiler, the sulfurcondenser configured to condense the elemental sulfur in cooled furnacestream to produce a liquid sulfur stream and a gas stream, wherein thegas stream is in the absence of elemental sulfur, wherein the gas streamcomprises water vapor; an adsorber fluidly connected to the sulfurcondenser, the adsorber configured to remove water vapor from the gasstream to produce a dry gas stream and a water stream, wherein theadsorber comprises a molecular sieve, wherein the dry gas streamcomprises hydrogen sulfide and sulfur dioxide and is in the absence ofwater vapor.
 12. The system of claim 11, further comprising: a firstClaus catalytic stage fluidly connected to the adsorber, the first Clauscatalytic stage configured to produce a first sulfur stream and a secondgas stream; a second Claus catalytic stage fluidly connected to thefirst Claus catalytic stage, the second Claus catalytic stage configuredto produce a second sulfur stream and a third gas stream; and a thirdClaus catalytic stage fluidly connected to the second Claus catalyticstage, the second Claus catalytic stage configured to produce a thirdsulfur stream and a tail gas stream.
 13. The system of claim 11, furthercomprising: a first Claus catalytic stage fluidly connected to theadsorber, the first Claus catalytic stage configured to produce a firstsulfur stream and a second gas stream; and a second Claus catalyticstage fluidly connected to the first Claus catalytic stage, the secondClaus catalytic stage configured to produce a second sulfur stream and atail gas stream.
 14. The system of claim 11, further comprising: a firstClaus catalytic stage fluidly connected to the adsorber, the first Clauscatalytic stage configured to produce a first sulfur stream and a secondgas stream; a second adsorber fluidly connected to the first Clauscatalytic stage, the second adsorber configured to remove water vaporfrom the second gas to produce a second dry gas stream, wherein thesecond adsorber comprises a molecular sieve, wherein the second dry gasstream comprises hydrogen sulfide and sulfur dioxide and is in theabsence of water vapor; a second Claus catalytic stage fluidly connectedto the second adsorber, the second Claus catalytic stage configured toproduce a second sulfur stream and a third gas stream; and a third Clauscatalytic stage fluidly connected to the second Claus catalytic stage,the third Claus catalytic stage configured to produce a third sulfurstream and a tail gas stream.
 15. The system of claim 11, furthercomprising a first Claus catalytic stage fluidly connected to theadsorber, the first Claus catalytic stage configured to produce a firstsulfur stream and a second gas stream; a second adsorber fluidlyconnected to the first Claus catalytic stage, the second adsorberconfigured to remove water vapor from the second gas to produce a seconddry gas stream, wherein the second adsorber comprises a molecular sieve,wherein the second dry gas stream comprises hydrogen sulfide and sulfurdioxide and is in the absence of water vapor; a second Claus catalyticstage fluidly connected to the second adsorber, the second Clauscatalytic stage configured to produce a second sulfur stream and a tailgas stream.
 16. A system to recover sulfur from hydrogen sulfide in anacid gas stream, the system comprising: a combustion furnace, thecombustion furnace configured to convert the hydrogen sulfide toelemental sulfur to produce a furnace outlet stream, wherein the furnaceoutlet stream comprises elemental sulfur, hydrogen sulfide, sulfurdioxide, and water vapor; a waste heat boiler fluidly connected to thecombustion furnace, the waste heat boiler configured to remove heat fromthe furnace outlet stream to produce a cooled furnace stream; a sulfurcondenser fluidly connected to the waste heat boiler, the sulfurcondenser configured to condense the elemental sulfur in cooled furnacestream to produce a liquid sulfur stream and a first gas stream, whereinthe gas stream is in the absence of elemental sulfur, wherein the firstgas stream comprises water vapor; a first Claus catalytic stage fluidlyconnected to the sulfur condenser, the first Claus catalytic stageconfigured to produce a first sulfur stream and a second gas stream; asecond Claus catalytic stage fluidly connected to the first Clauscatalytic stage, the second Claus catalytic stage configured to producea second sulfur stream and a third gas stream; an adsorber fluidlyconnected to the second Claus catalytic stage, the adsorber configuredto remove water vapor from the third gas stream to produce a dry gasstream, wherein the adsorber comprises a molecular sieve, wherein thedry gas stream comprises hydrogen sulfide and sulfur dioxide and is inthe absence of water vapor; and a third Claus catalytic stage fluidlyconnected to the adsorber, the third Claus catalytic stage configured toproduce a third sulfur stream and a tail gas stream.
 17. A system torecover sulfur from hydrogen sulfide in an acid gas stream, the systemcomprising: a combustion furnace, the combustion furnace configured toconvert the hydrogen sulfide to elemental sulfur to produce a furnaceoutlet stream, wherein the furnace outlet stream comprises elementalsulfur, hydrogen sulfide, sulfur dioxide, and water vapor; a waste heatboiler fluidly connected to the combustion furnace, the waste heatboiler configured to remove heat from the furnace outlet stream toproduce a cooled furnace stream; a sulfur condenser fluidly connected tothe waste heat boiler, the sulfur condenser configured to condense theelemental sulfur in cooled furnace stream to produce a liquid sulfurstream and a first gas stream, wherein the gas stream is in the absenceof elemental sulfur, wherein the first gas stream comprises water vapor;a first Claus catalytic stage fluidly connected to the sulfur condenser,the first Claus catalytic stage configured to produce a first sulfurstream and a second gas stream; an adsorber fluidly connected to thefirst Claus catalytic stage, the adsorber configured to remove watervapor from the second gas stream to produce a dry gas stream, whereinthe adsorber comprises a molecular sieve, wherein the dry gas streamcomprises hydrogen sulfide and sulfur dioxide and is in the absence ofwater vapor; and a second Claus catalytic stage fluidly connected to theadsorber, the second Claus catalytic stage configured to produce asecond sulfur stream and a tail gas stream.